Telegraph circuit monitoring device



Dec.' s, 1941.,

` H. o. ISI-:TERsoN TELEGRAPH CIRCUIT MONITORING DEVICE` Filed Jan. 28, 19523` INVENTOR PETERSON ATTORNEY vvvVvv' HARO I mummIf-uup lllhAAllll O l y Patented Dec. 30, 1941 Harold. 0. Peterson, Riverhead, N. Y., assignor to Radio. Corporationof America, a corporation of @menate i agpiicanenqanuafy 2s, 193s, serial No. 187,353

" .9 claims. (ci. 17a-.69.)

This invention relatesto monitoring devices andmore particularly to an Varrangernent for indicating abnormal conditionsv a telegraph'circuit or radio communications channel solthat `wlienthe signal departs fromaprescribed operating limits an indication `will will be sounded. i

It is an object of my invention to provide a monitoring device `for a telegraph circuit such that when the so-called marking elements of the received signals are compared with the spacing elements thereof in 4integrated time duration value and the relationship is foundfto be `abnormal; an alarm' or otherindicating device may be` actuated.

This invention is primarily applicable to radio telegraph circuits but may,` in some instances, be applied to cir-cuits carrying other forms of `coni- `munications. In telegraph circuits,i`the signal -is keyed in accordance with a telegraphfcode so@ that the signal consists of dots and dashes separated byspaces. In this specification the) term mark is used `to designate `thedots and dashes and the term space to designate the spaces'bei tween dots and dashes. It is` general' experience that in the handling of such communications `the summation of allthe dots and dashes is about equal to the summation of all the spaces; In other Words, under normal operating conditions the signal is on mark `about 50% 'ofthe time.` `Now if serious .interference occurs, some of the space intervals will contain energy andv the summation of mark Willbe abnormally high. If, on the other hand,- the" circuit is suiering from drop-outs or fading the summation of mark will beabnormally low. It is the purpose ofthe device herein described to detect and register when these abnormal conditions exist. i

`My invention will now be described in detail, reference being made to the accompanying drawing in which: i j

Figure 1 showsa circuit suitable for registering an abnormality in the telegraph line or radio channel whenever the percentage of mark Yis abnormally low, and

Fig. 2 showsla modification of the invention in which the alarm or. other indicating device is adapted to` respond Whenever the percentage of mark is. either too high on toolow.

Aswill be seen from the description to follow, the. devices shown in the two embodiments hereinlillustratively presented are sensitive tothe percentage of mark measuredin time, and. the Circuits. are designed tore. quiteindependenrof normal. variatie@ 11,1 theizealsreglitude l .l

be made or an alarm' Referring to Fig. 1, electronic device or tube 8 is normally biased to cut-01T by the D. C. drop in resistor 5. When the signal fed through transformer I` is on mark, tube 8 Will `draw plate current through resistor 2 and `will place a charge on condenser I0 such that the grid of electronic tube 9 is biased negative past `cut-olif. Condenser IU charges very quickly but discharges quite slowly. By proper choice of` constants assigned .to condenser I0 and resistor 2,\the time .required for discharge may bemade alvalue suitable to t the requirements. This time constant is ordinarily adjusted so that the normal space intervals` are not long enough to allow appreciable discharge of the voltage across condenser Ill. For this condition of regular and prescribed percentage mark, electronic tube il l.will remain biased to cut-off and zero plate current Willflow through relay II. II", however, the signal ceases `to `mark for a predetermined interval, condenser I0 willdischarge through resistor 2 and the grid f potential of electronic device 9 Willfassume such a Value that current will flow through relay II closing the Contact thereof which, in turn, causes current to flow through the coil of relay I2. When current flows through the coil of relay. I2 its contacts cause current to flow through indii cating lamp I6, alarm device I4 and the coil of special relay I3. The current to the alarm device I4 passes through the contacts of relay I3.

`Relay I3` may be provided with a` dash pot or other delay action so that afterfa few moments the circuit to alarm Mis broken,` to be restored I periodically after predetermined. intervals. of

time as long as energy is suppliedthrough the contacts of relay I2. 'i

Referring to Fig. 2, electronic device or tube 32 is normally biased to cut-off by the D. C. voltage Vdrop inv resistor I7. The resistor I1 forms part tive terminal of the direct current source and may, if desired, be grounded. A capacitor 2'! connected between the resistor 25 and choke 26 is oflarge value, and, being grounded to the `other `side, serves in combination with the choke V25 for smoothing out any ripple component, ifany, which may be present in the D. C. source. I

When `the signal. is on mark, tube. 32.draws "'Pllgl. Current. through resistor.. 43` and: charges of signal strength during the mark interval.

condenser 44 in such manner that electronic device 35 is biased to cut-off. This cut-olf bias reduces the direct current potential drop in resistor 46 to practically zero and consequently electronic device 36 will draw vplate current through resistor 49 thereby placing a negative low, electronic device 36 draws current a correspondingly lower percentage of the total elapsed time and consequently the average potential established on the grid of electronic device 3l will be less negative and more current will how through the coil of relay l causing its contacts to be yclosedand anindicator or alarm device 62 connected thereto will be operated.

Iny the samel circuit, when the signal is on mark, electronic device 32 draws current through resistor 43 causing electronic device 35 to be biased 'to cut-off with correspondingly small D. C. drop vin, resistor 4B. This condition of small drop in resistor `46 causes the grid of electronic device 53 to assume a potential which will cause plate current to flow through relay 52 and operate its associated indicating or alarm device 63. A time delay action is provided in the form of resistor l5 and condenser 54.

' The discharge tubes 31 and 53 are collaterally; l

' disposed in the nal stage of the cascaded network. These two tubes, however, are rendered conductive at mutually exclusive times due to the diierent preceding stages by which their grids are controlled. y

It should be noted that for the condition of mark the drop in resistors 49 and 46 is quite inl dependentof input signal strength. Also for the condition of space the D. C. potential drops in these two resistors are substantially independent By virtue of this keying action, time constant cirv cuits 48--50` andv I5-54 are substantially timeintegratingdevices so arranged that relay 5I will be caused to close its `contacts when the percentage of mark drops below a certain value, its

contacts remaining open for all valuesvof Vpercentage of mark above that predetermined value and the contacts of relay 52 will be caused to tube amplifier, responsive to mark and space signals, said amplier including two collaterally disposed discharge ytubes one of which is rendered conductive by an abnormal preponderance of marking signal time over spacing signal time and the other of which is rendered conductive by the abnormal preponderance of spacing signal time over marking signal time, means including a time constant circuit connected to said amplifier for integrating the time value of a succession of discrete mark signals received during a predetermined period, and means including an alarm signalling device responsive to the actuation of said collaterally disposed tubes for indicating aberrations of theintegrated marking signal time from a predetermined normal percentage of said predetermined period.

2. A system in accordance with claim 1 and including two distinguishing indicators in said alarm signalling device, one being responsive to an excess of integratedA marking signal time and the other responsive to a deciency in the same.

3. A telegraph signal monitoring device comprising at least four electron discharge tubes in combination with two condenser-resistor delay circuit devices, three of said tubes being arranged in cascaded stages and the fourth tube being in a stage having an output circuit in parallel with the output circuit of the final tube of said cas- Lput circuits of the third and fourth tubes for producing separate responses to an unbalance between marking and spacing intervals of the 4signals to be monitored, and distinctive indicating means operableunder control of said relay for producing indications of abnormal predominance of marking over spacing signals during a predetermined time interval in one instance and' an'opposite predominance during such a time interval in another` instance.

4. In a receiving telegraph system having a plurality of electron discharge tubes disposed in a cascaded network, the method of indicating aberrations from a normal ratio between the integrated time values of marking signalsv with re- "spect to spacing signals which comprises introclose only when the percentage mark exceeds ai" certain predetermined value. For example, in a typical application the constants werewadjusted so that relay 5| would close its contacts if the percentage mark became less than 25% for a period of over 10 seconds and the contacts of relay 52 would be closed if the percentage of mark exceededA 75% over a period of 10 seconds or more.

ItisV to be understood that variations in thel constructional details of my invention may be made and that the two embodiments of the invention asoillustrated in Figs. 1 and 2, respectively, are merely typical of devices of this character which are suitable for carrying out the stated primary object of the invention. The scope of the invention is, therefore, dei-ined by the claims to follow.

. I claim:

l. A monitoring system for telegraph circuits comprising a low frequency electron discharge ducing a retardation effect in the control of one tube in the nal stage of saidnetwork in response to variationsin the conductivity ofthe tube in the preceding stage, whereby the tube in the final stage becomes conductive only when Vthe ratio of marking to spacing signal time drops below a prescribed operating limit, introducing a retardation effect in the control of a collaterally disposed tube in the nal stage of said network in response to variations in the conductivity of tubes in s'aid nal stage becomes conductive.

V5. In a receiving telegraph system having an arrangement of three electron discharge tubes in a cascaded network and a fourth tubein parallel with the tube in the final stageof said network,

each of said tubes being controllable by grid bias variations, said fourth tube being controlled directly by the output energy from the tube in the rst stage of said network, the method of indicating aberrations from a normal ratio between marking and spacing signals which comprises introducing retardation effects in the control of the tube in the final stage and also in the control of said fourth tube, rendering the tube in the first stage conductive only in response to spacing signals, adjusting the control bias on the tubes of said cascaded network so that the tube in the final stage is rendered conductive only when the ratio of marking to spacing signals falls below a prescribed operating limit, adjusting the bias on said fourth tube so that it is rendered conductive only when said ratio exceeds another prescribed operating limit, and producin'g an alarm signal which is distinctive in respect to the particular tube thus rendered conductive in response to the retardation effect.

6. The method as set forth in claim 5 and including the further step of rendering said alarm signal intermittent.

7. A monitoring system for a telegraph circuit, comprising an electron discharge tube amplifier responsive to mark and space signals, means including time-constant cir-cuits connected bei tween stages of said amplier for rapidly accumulating energy charges in proportion to the marking signal time and for slowly dissipating l such charges in proportion to the spacing signal time, said means being capable of integrating said charges during la period which covers the reception of a succession of discrete marking impulses, said ampliiier including two collaterally disposed discharge tubes one of which is rendered conductive by an abnormal preponderance of Cil marking signal time over spacing signal time and the other of which is rendered conductive by an abnormal preponderance of spacing signal time over marking signal time, said collaterally disposed electron discharge tubes having input circuits whose control :bias is maintained below cutoff by an accumulation of energy charges in said time constant circuit under conditions of normal traino code signaling.

8. A system in accordance with claim 7 and including an alarm device operable in responseV to current flowing through either of said discharge tubes.

9. A system for monitoring keyed telegraph signals comprising a first discharge tube having an input circuit and anoutput circuit, a time constant device in said input circuit, a second discharge tube under control of voltage variations in the output circuit of said first discharge tube, a third and a fourth discharge tube each having a separate input circuit characterized by the inclusion of a time constant device, the third tube being rcontrolled b-y output voltages from said second discharge tube, the fourth tube being controlled by output voltages from said first discharge tube, a three-position relay having opposing windingsone of saidwindings being connected in an output circuit of said third tube, the other of said windings being connected in an output` circuit of said fourth tube, and means responsive to the actuation of said relay for indicating departures in one direction and in the opposite direction from a normal ratio between the integrated time intervals representing marking and spacing pulses respectively of a telegraph message whose marking impulses are impressed on the input circuit of said first discharge tube. yHAROLD O. PETERSON. 

